1. Field of the Invention
The present invention relates to a resin film evaluation method which allows for efficient evaluation of the degree of degeneration of a treated resin film and its removal properties after treating a semiconductor substrate with charged energetic particles using as a mask a resin film including a photosensitive resin film such as a photoresist film, for example, in the manufacturing process of a semiconductor integrated circuit device. And the present invention relates to method for manufacturing a semiconductor device applying the resin film evaluation method.
2. Description of the Related Art
In the manufacturing process of a semiconductor device such as a semiconductor integrated circuit device, it is a common technique to form a pattern of photosensitive resin film such as a photoresist film on a semiconductor substrate and use the pattern as a mask. For example, the pattern is used as a mask to implant impurities such as phosphorus, boron, or arsenic in the semiconductor substrate in ion implantation. Then, for example, the source/drain region and drain extension region of a MOS (metal oxide semiconductor) transistor are formed. In dry etching, the underlying film or semiconductor substrate is exposed to etching gas plasma as the pattern is used as a mask. Then, the underlying film or semiconductor substrate is processed to have a form according to the pattern.
The photoresist film used as a mask in such ion implantation or dry etching is subject to ion bombardment from ions in the ion implantation or plasma in the dry etching. Meanwhile, the surface of the photoresist film is hardened or degenerated. The more ion bombardment the photoresist is subject to, the more the surface is hardened or degenerated (for example, see Japanese Patent Application Publication Nos. H6-252042 and 2004-191833).
When a layer hardened or degenerated as described above (termed the degenerated layer hereafter) is formed on the surface of the photoresist film, it becomes difficult to remove the photoresist film when the implantation dose is high. A sulfuric acid-hydrogen peroxide mixture (SPM) at approximately 140° C. is extensively used in order to remove the photoresist film (to rinse the semiconductor substrate). However, the photoresist film may not be completely removed only by the SPM. Therefore, in order to remove the photoresist film used as a mask in the ion implantation, the photoresist film is first removed by a down flow of isotropic oxygen plasma and then the semiconductor substrate is thoroughly rinsed with the SPM. In this way, the semiconductor substrate having no photoresist film residue is further processed.
In the general manufacturing process of a semiconductor device, the photoresist film removal procedure and concrete process conditions are not changed once they are determined. On the other hand, the degree of hardening or degeneration of the resin film including photoresist films is evaluated for the purpose of determining the photoresist film removal conditions. The resin film evaluation is performed as follows.
FIGS. 14A to 14E show cross-sectional views for explaining the extensively used prior art resin film evaluation method. As shown in FIG. 14A, a desired film 102 such as a silicon oxide film and a photoresist film 103 are formed on a silicon substrate 101 in this order from the bottom. Then, as shown in FIG. 14B, the photoresist film 103 is exposed to exposure light 105 such as an ultraviolet, electron, or X ray via a reticle 104 having a desired pattern. The exposed photoresist film 103 is developed, rinsed with purified water, and post-baked to have the photoresist film 103 patterned as shown in FIG. 14C. Subsequently, as shown in FIG. 14D, ions 106 such as phosphorus, boron, or arsenic are implanted in the semiconductor substrate 101 by ion implantation using the pattern as a mask. Here, the surface layer of the photoresist film 103 where the ions 106 are implanted forms a degenerated layer 112 of which the molecular structure is different from that of the deep part. Then, the above described oxygen plasma treatment and SPM rinsing are performed to remove the photoresist film 103 as shown in FIG. 14E.
After the rinsing, the photoresist-removed surface is irradiated with a laser beam 110 and light reflected by resist residues 111 (or light scattered by the resist residues 111) is detected to determine a particle count. The particle count determined in this way is an indicator of the degrees of hardening or degeneration of the degenerated layer 112 formed on the surface of the photoresist film 103 provided that the photoresist film 103 is removed under given conditions. When the ion implantation is performed under given conditions, the particle count is an indicator of the resist removal ability of the removal conditions applied to the photoresist film 103 including the degenerated layer 112. In this way, the degrees of hardening or degeneration and removal property of a resin film can be evaluated.
The above evaluation method is similarly applicable where ion implantation shown in FIG. 14D is replaced with dry etching such as plasma etching. In such a case, the degree of hardening or degeneration of the degenerated layer formed in the surface layer of the photoresist film 103 as a result of exposure to etching gas plasma and the removal property of the plasma-etched photoresist film 103 can be evaluated based on the particle count.
In the manufacturing process of a semiconductor integrated circuit device, the removal of resin films such as photoresist films is checked by the above described evaluation method usually on an irregular basis if it is checked. In some cases, the shrinkage of the resist in association with the formation of a degenerated layer is determined by measuring an SEM (scanning electron microscopy) image for evaluating the degree of degeneration during the dry etching.